In the absence
of or unavailability of such a central computer system, the component sharing method can
be used as a backup or alternative procedure to keep the system running. For example, a
reader installed in a new location could contact its nearest operational reader using this
scheme to download the most popular communication environment variables used in that
area. These settings would include information such as available frequency allocation,
bandwidth, average number of tags per unit of time, number of readers and their locations,
noise conditions, etc. This information can be used to optimize communications. This
scheme therefore can tremendously increase the ?¬‚exibility of an RIFD system. Such
functionality is not available currently in any RFID system.
5.1.5 Software versus Hardware
A traditional radio receiver requires many analog components, as shown in Figure 5.1.
First the radio signal is received by the antenna and is then ampli?¬?ed by an LNA (low noise
ampli?¬?er). These parts are shared by all the radio channels (Brannon, 1995). After these
components one receiver is required for each channel. The RF signal is down converted to
baseband by a mixer and a local oscillator. At each stage analog ?¬?lters are used to
discriminate the signal outside the frequency band. The last step before the digitization
96 RFID Handbook: Applications, Technology, Security, and Privacy
is to decompose the signal into inphase and quadrature components.
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